(1) Field of the Invention
This invention relates to a novel water-soluble resin. In particular, this invention relates to a water-soluble resin for packaging ink, derived from the reaction product of a modified rosin and a bis (secondary amine) such as piperazine.
(2) Description of Prior Art
Resin used as a vehicle for water based packaging ink must exhibit properties such as solubility in water, wet adhesion to polypropylene film, hydrolytic stability, high melting point, and good pigment wetting.
Alcohol soluble polyamide resins have been used extensively in inks for packaging and are commercially available. These polyamides are made from dimerized fatty acids and various polyamines such as ethylene diamine or hexamethylene diamine.
The use of such polyamide resins in ink compositions is described in Floyd, D. E., Polyamide Resins, Reinhold Publishing Co., New York, 1958 and in the Encyclopedia of Polymer Science and Technology. Interscience Publishers, John Wiley Sons, Volume 10, New York, 1969. A typical commercial product is GAX-340 manufactured by Henkel.
For water based ink, a water soluble -resin such as acrylic resin or a conventional soluble maleic resin may be used. Acrylic resins have good film properties, but lack adhesion to polyolefin films.
Conventional soluble maleic resins, which contain halfesters, are subject to a certain degree of hydrolytic instability under alkaline conditions. They also lack film toughness.
It is therefore the object of this invention to provide a novel water soluble resin having qualities of adhesion, wettability and stability for use in packaging ink compositions.